585
J. Org. Chem. 1986,51, 585-589
High-pressure Addition Reactions Involving Cycloheptatriene-Norcaradiene Equilibrium GBrard Jenner* and Mihail Papadopoulos Laboratoire de Pilzochimie, Chimie Organique Appliqule, ENSCS, Universiti Louis Pasteur, 67008 Strasbourg, France Received M a y 29,1985
Several high-pressure reactions of cycloheptatriene(CHT) were investigated with various unsaturated compounds. M, , N=N), norcaradiene adducts were formed, whereas with the unsymmetrical With homonuclear bonds (M C=O bond, only ene-type addition was observed. There is a general tendency to form norcaradiene adducts under high pressure (reactions of CHT with acrylonitrile and acetylenic bonds). Several unprecedented peculiar features are observed under pressure: inter- and intramolecular formation of the norcaradiene adduct (CHTdimethyl acetylenedicarboxylate), homo-Diels-Alder reactions involving bicycloodadiene systems (CHT-methyl propiolate), formation of the unknown norcaradiene adduct with the N-N fragment (CHT-diethyl azodicarboxylate) showing interesting NMR properties reflecting conformational changes.
The ring inversion and cyclotautomerization processes Scheme I are interesting properties of the cycloheptatriene structure. While the ring inversion is generally so rapid that it could be observed only at very low temperatures,'I2 the valence isomerization cycloheptatriene-norcaradiene3 can be evidenced even at relatively high temperatures via the reaction products (Scheme I).4 A t the usual temperatures needed to achieve these reactions, norcaradiene can exist only as a transient molecule? Considering that norcaradiene adducts are f o ~ n e d ~ * ~ with 100% yield after a couple of hours. at temperatures as high as 120-180 "C, it is evident that 2. Reaction with Acrylic Esters. The reaction of the diene is an extremely reactive molecule in comparison CHT with acrylonitrile and methyl acrylate were studied with cycloheptatriene (CHT)? However, products derived at atmospheric pressure under high-temperature condifrom [6 41 cycloaddition and ene reaction on the CHT tions (170-200 "C, 18-24 h).7 ring are usually also o b s e r ~ e d ,especially ~,~ at high temThey give several products which were identified (in peratures. We thought that such reactions would be addition to CHT dimers) as norcaradiene adducts 1 and susceptible to be minimized when the temperature is 2 and as the product 3 resulting from a formal l,6-addilowered. However, this procedure introduces a beneficial tion." 1-3 were produced in a 9:9:2 ratio (when X = CN) effect on norcaradiene reactions, only if the system keeps and a 2:ll:l ratio (when X = C02CH3). sufficient reactivity. In this respect, we were prompted to use high pressures, since it is a common feature that addition reactions with volumes of activation in the order of -30 to -50 mL/mol are greatly facilitated by the application of pressure, if concertedness is proved? The aim 3 of this paper is to examine the pressure effect on the 2 1 product distribution in some reactions between CHT and Repeating these experiments in CH2C12at ambient multiple homo- or heteronuclear activated bonds (C=C, pressure in the temperature range of 160-180 OC (24 h), CEC, N=N, C=O). we found following ratios: when X = CN, 1:2:3 = 4:4:1, 1. Reaction with Tetracyanoethylene. The reaction total yield 65%; when X = CO2CH3,1:2:3 = 3:12:1, total of CHT with the reactive TCNE is known to produce only yield 38%. one 1:l adduct whose formation has been rationalized in Under 900 MPa at 80 "C, only 1 and 2 were produced terms of the Diels-Alder reaction involving the norin the ratio 1:l when X = CN and 1:5 when X = C02CH3. caradiene form.1° No trace of 3 nor dimers of CHT could be detected. Yields Under high pressure (900 MPa) at ambient temperature, were respectively 80% and 62% (reaction time, 24 h). In the norcaradiene adduct was formed as unique product order to verify whether 3 transforms into norcaradiene adducts, we submitted to 900 MPa (80 OC) the adduct mixture (free from reactants) resulting from the atmos(1) Anet, F. A. J. Am. Chem. SOC.1964,86, 458. ( 2 ) Takeuchi, K.; Kitagawa, T.; Senzaki, Y.;Okamoto,K. Chem. Lett. pheric runs. No change in the composition of the mixture 1983, 73. occurred. (3) Hoffmann, R. Tetrahedron Lett. 1970, 2907. This study shows that, under high pressure and at (4) The tricyclic adduct retaining the norcaradiene unit can theoretically also be formed via a [4 + 21 homocycloaddition to cycloheptatriene: moderate temperatures, the CHT-acrylic esters reactions Balci, M.; Atasoy, B. Tetrahedron Lett. 1984, 25, 4033. lead selectively to norcaradiene adducts in agreement with (5) Norcaradiene has been isolated by a matrix technics at -196 O C : our initial hypothesis. In addition, it should be remarked Rubin, M. J. Am. Chem. SOC. 1981,104, 7791.
+
r"
(6) Goldstein, M. J.; Gevirtz, A. H. Tetrahedron Lett. 1965, 4413. (7) BelluH, D.; Helferich, G.; Weis, C. D. Helu. Chim. Acta 1971, 54, 463. (8) Friedman, P. K.; Balls, D. M.; Brown, D. J. J. Org. Chem. 1968, 33, 2211. (9) Jenner, G. Bull. Soc. Chim. Fr. 1984, 275. (10)Wahl, G. H. J. Org. Chem. 1968,33, 2158.
0022-326318611951-0585$01.50/0
N
&
(11) Bellui claimed 3 to be the endo isomer. However, the NMR spectrum clearly shows that 3 is a mixture endo + exo (the relative proportions could not be determined), since no full decoupling could be made by irradiation. Besides the NMR data in ref 7 are incorrect. The complete 6 values are reported in the Experimental Section of this paper.
0 1986 American Chemical Sociatv
586 J . Org. Chem., Vol. 51, No. 5, 1986
Jenner and Papadopoulos Scheme I1
Table I. Pressure Effect on Product Distribution" P , MPa
time, h
% 4
% 5
0.1 100 200 400
8-48
68 73 78 82 90 90 95 97 99 100
32 27
6-20 15 1 5
400 400
16 5.5
600 800 800 900
3
15 1
22
10 10 5 3 1
0
that pressure does not affect the exo-endo ratio in accordance with a previous finding.12 3. Reaction with Dimethyl Acetylenedicarboxylate. The reaction was studied a long time ago6 in refluxing toluene. Two adducts 4 and 5 in the ratio 2:l (total yield, 38%) are formed. The major product 4 was shown to be the norcaradiene adduct, whereas 5 was the result of an ene-type addition (see Scheme 11) (E = CO,CH,).
Application of 900 MPa of pressure at room temperature during one day yielded 4 as the only product in 16% yield. Total conversion occurred by heating a touene or a CHzClz solution of reactants at 80 "C (900 MPa, 15 h), giving again exclusively 4 despite the higher temperature. It was obviously of interest to examine the temperature and the pressure effect on the formation of 4 and 5. Examination of the temperature dependence (in the range 70-120 "C) of the second-order rate ~onstants'~ gave linear Arrhenius plots yielding the following (the subscript refers to the corresponding adduct): E4 = 81.9 kJ/mol E5 = 79.0 kJ/mol AS4* = -156.7 kJ/mol.K
A5 = 1.18 X lo5
AS5* = -157.2 kJ/mol.K
Visibly the formation of both adducts show similar temperature dependence. Additionally we have verified that there was no interconversion of products in the examined temperature range. The kinetics13was further followed in the low-pressure region (0-120 MPa) at 96.5 OC. Application of the transition-state theory leads to the determination of the apparent volumes of activation: AV5* = -28.8 mL/mol AV4* = -33.8 mL/mol If the mechanism for each reaction is not altered by the pressure, the application of Elyanov's selectivity relationship,14
a
- In ( k 4 / k 5 )= aP
E
+ E
18
"At 80 O C , in CH2C12solution.
A4 = 1.20 X lo5
0 -
AV,' -AV5'
RT
(@ is a function of pressure, independent on reaction;
the exponents p and 0 refer to pressure p and 0.1 MPa) (12)Seguchi, K.; Sera, S.; Maruyama, K. Tetrahedron Lett. 1973, 1585. (13)Kinetic values are available upon request. (14)Elyanov, B. S.;Gonikberg, M. G. Izv. Akad. Nauk SSSR,Ser. Khim. 1967,1044.
should give (for example, for p = 800 MPa, 9 = 24.3) 74% of 4 and 26% of 5. However, the 800-MPa run showed selectivities for 5 as low as 3% after 3 h of reaction and 1% after 15 h; Table I reports the pressure effect on product distribution. These results indicate a time dependence of the product ratio above 100 MPa. There is a detrimental pressure effect on the formation of 5 which ultimately vanishes at a sufficient high pressure. Adduct 5 is believed to form sequentially6 (Scheme 11). The first step in this sequence is an ene reaction which should be considerably accelerated by pressure providing full con~ertedness.'~The last step (7 5 ) considers a (3,3)-sigmatropic process for which the volume of activation has been reported as negative.16 Pressure should therefore also accelerate the formation of 5 , probably to the same extent as for 4, as is inferred by the fairly negative value of AV,'. At higher pressures, there could be a subsequent reaction involving 5 (homo-(l,5)-sigmatropicshift and skeletal rearrangement to form 4). However, it is also possible that the course of the reaction is altered during the formation process of 5. We therefore submitted a 65:35 mixture of 4 + 5 to 1100 MPa of pressure at 85 "C during 18 h. The ratio changed to 69:31 only. The result is not convincing regarding a possible transformation of 5 into 4. Therefore, to account for the exclusive formation of 4 at the higher pressures, we propose the sequential process 7 8 4 (Scheme 11). The norcaradiene intermediate 7 is thus presumed to be reactive enough under high pressure to undergo an intramolecular [4 + 21 reaction to give the highly strained caged molecule 8 which eventually rearranges into 4. According to this proposal, the volume of activation of the intramolecular Diels-Alder process should exhibit a much higher absolute value than the AV* for the (3,3)-sigmatropic shift.I7 Again, as in the reaction involving acrylic esters, high pressure makes the reaction between CHT and the acetylenic diester very selective toward the norcaradiene adduct. 4. &action with Methyl Propiolate. This acetylenic monoester was allowed to react with CHT in high-pressure conditions, since at ambient pressure and at 180 "C, the reaction gave numerow unidentified products in poor yield (about 5 4 % ) . Compared to the diester, the acetylenic bond in methyl propiolate was less reactive: at 80 "C under 900 MPa, the product yield was 73% (after 68 h) (cf. with the 100% conversion after 15 h in the former case). As exposed previously,'* four products were formed, all exhibiting the norcaradiene structure (E = CO,CH,).
-
--
(15)Jenner, G.; Papadopoulos, M. J. Org. Chem. 1982,47,4201. (16)Claisen and Cope rearrangements have negative AV* (-5to -15 mL/mol): (a) Brower, K. R. J. Am. Chem. SOC. 1961,83, 4370. (b) Walling, C.; Naiman, M. J. Am. Chem. SOC.1962,84,2628. However, other sigmatropic shifts were described as stepwise processes: le Noble, W. J.; Daka, M. R. J.Am. Chem. Soc. 1978,100,5961. (17) A value of -25 mL/mol was reported for an intramolecular Diels-Alder reaction: Isaacs, N. S.; van der Beeke, P. Tetrahedron Lett. 1982,23,2147. (18)Papadopoulos, M.; Jenner, G. Tetrahedron Lett. 1985,26,3335.
J. Org. Chem., Vol. 51, No. 5, 1986
High-pressure Addition Reactions 11 and 12 are polyadducts resulting from a further 1,4addition of the acetylenic bond to the norcaradiene adducts 9 and 10, respectively. These additions occur only under
587
Scheme 111
E .E E
9,
10 c
RE
?+E 12 N
high pressure and provide examples for an extension of the synthetic possibilities of the homo-Diels-Alder reaction to bicyclooctadiene systems. Another point to be outlined is that, while 9 is the product of the typical [4 + 21 cycloaddition, 10 results from the [4 + 21 addition of methyl propiolate on the initial ene monoadduct in equilibrium with the corresponding norcaradiene 13.
13 The relative proportion of 9 11 vs. 10 12 is 2:1, e.g., the same ratio as with the acetylenic diester. However, in the present case, the reactivity of the external double bond in 13 is different (compared to 7); 13 prefers to undergo an intermolecular [4 21 cycloaddition rather than to react in an intramolecular way. 5. Reaction with Diethyl Azodicarboxylate. The reaction was investigated by Cinnamon and we is^'^ who detected an adduct 14 resulting from an ene process. The reaction was further investigated with cycloheptatriene-7-d and the suggestion was made that the ene reaction could involve not only a six-membered but also a ten-membered transition stateaZ0 Since ene and (4 2) addition seem to be equally accelerated by pressure9J6(see also reaction 3), it was not evident whether pressure will promote the norcaradiene addition. Under high pressure (900 MPa) at ambient temperature, three compounds in the ratio 2:l:l were detected by gas chromatography. Conversion of the azo diester was 100% within 3-5 h. The main product was shown to be the expected ene compound 14 (E' = COzCzH6). The two others were separated and characterized as the norcaradiene adduct 15 and 1,2-dicarbethoxyhydrazine16. The latter is known to form easily in reactions involving azodicarboxylates.21
+
+
+
+
At ambient pressure, 15 is not produced, whereas 16 is formed with a low yield, although it was not reported in the former study.Ig Thus, again, pressure has a beneficial effect on the formation of the norcaradiene addition product. It is interesting to note that the ratio 15:14 here is 1:2 (the inverse of the value found in the CHT reactions involving acetylenic esters), due to the enophilic character of the diazene ester. The new adduct 15 possesses peculiar NMR properties which are reported below. The 'H NMR spectrum recorded at ambient temperature shows two distinct vinylic protons, each of them resolved as a triplet, suggesting a (19) Cinnamon, J. M.; Weiss, K. J. Org. Chem. 1961,26, 2644. (20) E. Koerner von Gustorf cited by: Hoffmann, H. M. R. Angew. Chem. 1969,81, 597; Angew. Chem., Int. Ed. Engl. 1969,8, 566. (21) (a) Shah, A.; George, M. V. Tetrahedron 1971, 27, 1291. (b) Franzus, B. J. Org. Chem. 1963,28, 2954.
Table 11. Interconversion Barriers and Flexibility Indexes AGgg*: compd Act,. kJ/mol kJ/mol flexibility* ref
78.2
76.1
0.80
this work
Since T , depends on compound and type of signals which collapse (E or vinylic protons), the AGc* values were standardized for T = 80 O C . bDefined as the ratio AG*(compound):AG*(reference) at 80 "C.
molecular dissymmetry. A variable-temperature NMR study revealed that both triplets transform into broad signals and eventually collapse into a unique triplet at 90 f 2 "C. Taking into account earlier conformational studies22 involving [2.2.n] bicyclic systems containing also the fragment NE-NE, we ascribe the phenomenon to conformational changes (preference for a twisted conformation, which was clearly detected in bicyclic systems, with n = 2)22(Scheme 111). The origin of the two distinct signals for the vinylic protons results from an out-of-plane structure for the N-N fragment. Lehn presented a method permitting to calculate approximate values of the barriers hindering the above interconversi~n:~~ AGS = 4.57Tc[9.7+ log Tc/Av] where T, is the coalescence temperature and Av is the separation of the signals. Av is correlated with the rate constant of the process. In the related paper,22Lehn defined for the investigated bicyclic systems a "flexibility index" (reference: N,N'dibenzyl-N,N'-dicarbomethoxyhydrazine)which is believed to be a measure of the height of the energy barrier relative to the considered interconversion: the lower the flexibility, the higher the rigidity of the system and therefore the lower the interconversion barrier (Table 11). As clearly shown in Table 11, the compound 15 fits fairly well the general trend. The AG* value and the flexibility number for 15 are intermediate between the corresponding values for the [2.2.2] and the [2.2.3] systems. Compared to the latter, AG,,* for 15 is lowered by 5.4 kJ/mol, due to the presence of the rigid cyclopropane ring. 6. Reaction with Dimethyl Mesoxalate. Activated carbonyl bonds are much less reactive than activated C 4 , C=C, and N=N bonds. The unprecedented reaction between CHT and dimethyl or diethyl mesoxalate does not occur at normal pressure (at least up to 140 "C). Submitted to high pressure (950 MPa) at 80 "C, the reaction (22) Lehn, J. M.; Wagner, J. Tetrahedron 1969, 25, 677. (23) (a) Lindscheid, P.; Lehn, J. M. Bull. SOC.Chim. Fr. 1967,992. (b) Anderson, J. E.; Lehn, J. M. Tetrahedron 1968,24, 123. ( c ) Anderson, J. E.; Lehn, J. M. J.Am. Chem. SOC.1968,89, 81.
588 J. Org. Chem., Vol. 51, No. 5, 1986
affords two products in the ratio 95:5 (72% yield after 24 h). The dominant product 17 was shown to be the ene adduct (E = CO,CH,). o ; - oE n /
Jenner and Papadopoulos mg of hydroquinone in a small autoclave at 160-180 "C. After reaction and GLC analysis ( t R : 1, 13.42; 2, 14.46; 3, 14.94), the solvent was removed and the residue placed onto a silica gel column. Elution with hexane-ether (7525) yielded 1 ( R f0.27), 2 (R, 0.16), and 3 (Rf0.12 as a mixture of endo and exo isomers). The spectra were given previ~usly.~ The spectrum of 3 is as follows:
The other product could not be separated from 17. No norcaradiene structure, however, could be evidenced. This is not surprising in view of the electronic dissymmetry of the C=O bond in the mesoxalate molecule which behaves as a remarkably good e n ~ p h i l e . ' ~ , ~ * 1
Conclusion Application of high pressure is an effective way to increase the reactivity of the cycloheptatriene system. The large negative volumes of activation are in agreement with concerted reactions enabling the use of lower temperatures and leading to [4 + 21 and [2 + 2 + 21 cycloadditions when feasible. The net effect is that adducts retaining the norcaradiene structure are selectively produced under pressure, especially when reactive symmetrical bonds (C=C, C=C) are involved. With the N=N bond, the norcaradiene adduct, which is not formed under normal pressure conditions, is produced in fair amount at high pressure. With the less reactive unsymmetrical C=O bond, only hydrogen abstraction takes place. The examples shown in this paper can be extended to other reactive bonds (some are under investigation) and demonstrate the synthetic utility of high pressure in generating new compounds. Experimental Section General. CH2Clzand toluene were dried and distilled prior to use. Cycloheptatriene and the titled dienophiles were distilled under vacuum. Dimethyl mesoxalate was prepared as previously de~cribed.'~ Melting points (mp) were determined with a Reichert hot stage microscope (mp uncorrected). Routine GLC analyses were performed in the following conditions: IGC 120 instrument (catharometer; He as gas carrier; program 60-230 "C, 8 OC/min) with columns FFAP (reaction 2), OV210 (reactions 3 and 4), Apiezon (reaction 5), and SE 30 (reaction 6). High-resolution GLC analyses were carried out on a Hewlett-Packard 5880 A instrument (FID; Nz as gas carrier; column, capillary fused silica cross-linked 5% phenylmethylsilicone, 0.2 mm X 12.5 m; program 50-210 "C, 5 OC/min). The retention time values (tR) for products refer to this column. The kinetics of reaction 3 was followed in the usual way'5 by GLC (column OV210 and 1,2,3,4-tetramethylbenzeneas standard). TLC was performed on silica gel 60GF254 (Merck) and preparative-layer chromatography on silica gel 60 (Merck 9285, 230-400 mesh) (2-mm thickness). R, values refer to silica gel and corresponding eluent system. 'H NMR spectra were taken with a Varian XL 100 spectrometer. Fine resolution was achieved with a Brucker WH-360 instrument (Me4Si as standard, chemical shifts in ppm, coupling constants in Hz). Mass spectra were recorded with a CH-4 MAT instrument and IR spectra with Perkin-Elmer spectrometer. 1. Reaction with Tetracyanoethylene. TCNE (100 mg, 0.78 mmol) was dissolved in 2 mL of CH&N. After addition of 90 mg (0.98 mmol) of CHT, the reaction tube was closed and introduced into a high-pressure vessel kept at room temperature. After reaction, the solvent and CHT were removed and pure 7,7,8,8-tetracyanotricyclo[3.2.2.0~44]non-6-ene'0 as shown by NMR was isolated. 2. Reaction with Acrylonitrile. The reaction was conducted at atmospheric pressure on a CHzCl2 solution of 450 mg (4.90 mmol) of CHT and 400 mg (7.54 mmol) of acrylonitrile with 10 (24) (a) Achmatowicz, 0.; Pietraskiewicz,M. Tetrahedron Lett. 1981,
22, 4323. (b) Jenner, G.; Papadopoulos, M.; Jurczak, J.; Koiluk, T. Tetrahedron Lett. 1984,25,5747. (c) Papadopoulos, M.; Jenner, G. Nouu. J . Chirn. 1984, 8, 729.
CN
'H NMR (CDCl3) 6.87 (9, H-1, J1,z = 11,51,7 = 8-59J I , ~ I), 6.00 (q, H-4, J3,4= 11, 54,5 = 6, J2,4 11, 5.97 (t, H-2 and H-3, J3,4 = 11,J2,, = 6.6, J 2 , 4 = l),2.94 (m, H-7, J 1 , 7 = 8.5), 2.78 (m, H-5, J4,5 = 6), 2.35 (m, H-gx, J9,9 = 13.5), 2.17 (m, H-gn), 2.08 (m, H-6s and H-6a). 3. Reaction with Dimethyl Acetylenedicarboxylate. A toluene solution (2.5 mL) of 540 mg (5.86 mmol) of CHT and 694 mg (4.88 mmol) of the acetylenic compound was introduced into a small autoclave and heated at 120 "C under atmosphericpressure during 110 h. After reaction, the solvent was evaporated and excess CHT removed by short-path distillation. GLC analysis showed the presence of two products 4 ( t R 22.81) and 5 (tR23.35). Column chromatography using hexane-ethanol (9O:lO) as eluent led to the separation of 4 (Rf 0.27) and 5 (R, 0.21), which were easily proved to be identical with those reported in the literature! 4. Reaction with Methyl Propiolate. A solution of 215 mg (2.56 mmol) of methyl propiolate and 285 mg (3.10 mmol) of CHT in CH2C12(2 mL) was heated at 170-180 OC during 1 day. GLC analysis showed the formation of at least 10 products (overall conversion: 5-8%), which were not separated. The high-pressure reaction (900 MPa, 80 "C, 68 h) was performed with 688 mg (8.19 mmol) of methyl propiolate and 1100 mg (11.96 mmol) of CHT in CH2C12(1 mL). GLC analysis revealed the presence of four products (overall yield 73%). Column chromatography with hexane-ether (3:2) as eluent separated 9 (R, 0.52), 10 + 11 (R, 0.30), and 12 (R, 0.15). To resolve 10 and 11, a second chromatography was necessary with hexane-ethyl acetate (4:l) (R, 0.26 for 10 and R, 0.20 for 11). (a) Adduct 9:
liquid; t R 13.8 IR (CDCl3)3090,3050,3025,2980,1730,1640,1605 cm-'; NMR 7.54 (dd, H-2, J 2 , 3 = 6, J2,6 = 15), 6.02 (dt, H-5, J 5 , 6 = 6,J4,5 = 7,J3,5 = 1.5), 5.92 (dt, H-4, J3,4 = 6, J 4 , 5 = 7, 54,6 = 1.5), 4.17 (m, H-6, J6,5 = 6, J66,7 = 3, J6,2= 36,4 = L5), 3.73 (m, H-3, 5 3 , 4 = J2,,= 6, J3,8= 3, J3,5= 1.5), 3.10 (s, OCH3), 1.26 (m, H-7, J7,e = J7,ga = 7, J7,%= 3.5, J7,6 = 31, 1.15 (m, H-8,57,8= J ~ , 9 a = 7, Js.9s = 3.5, J 8 , 3 = 31, 0.78 (dt, H-9, Jga,gs = 6, J8,gS = J7,9s = 3.5), 0.54 (dt, H-ga, J7,9a = J8,ga = 7, J9a,9s = 6). Anal. Calcd for C11H1202: C, 74.98; H, 6.86. Found: C, 74.50; H, 6.70. (b) Adduct 10:
4
2
solid; mp >300 "C; t R 21.8; IR (CDC13) 3070,3040,1720,1645cm-'; NMR (when not indicated, coupling constants are similar to those given for the corresponding protons in 9) 7.53 (dd, H-2), 6.52 (dd, H-10, Jlo,ll = 16, J g , l o = lo), 6.13 (dt, H-5), 6.04 (dt, H-4), 5.71 (d, H-11, Jlo,ll = 16),4.33 (m, H-6, J6,?= 4.51, 3.94 (m, H-3,53,8 = 4.5), 3.72 (d, OCH, on C-l), 3.67 (s, OCH3 on C-ll), 1.76 (dt, H-9, J g , l o = 10, J7,9 = J8,9 = 2.8), 1.59 (m, H-7, J7,8 = 8.5, 5 6 , ~= 4.5, J7,9= 2.8), 1.50 (m, H-8, J7,*= 8.5, J3,8= 4.5, J8,9 = 2.8) [the trans structure for H-10 and H-11 is substantiated by the coupling = 16 Hz; the constant J9,10 = 10 Hz represents a constant JlO,''
J. Org. Chem. 1986,51, 589-592 mean value for the rotation around the bond Cg-Clo];MS, m l e 260, 245,228, 196, 169, 141, 128. Anal. Calcd for C14H1604:C, 69.22; H, 6.20. Found: C, 69.08; H, 6.11. (c) Adduct 11:
8
COzCH
CH,CO,
11
12
solid, mp > 300 "c;tR 20.1; IR (CDCl,) 3035, 3020, 1720, 1590 cm-'; NMR (7.42 (d, H-12, Jz,lz= 3), 3.72 (8, OCH, on C-13), 3.65 (s, OCH, on C-1), 3.12 (dt, H-2, J2,, = 1.5, J2,4 = 1.8), 2.92 (br, H-4, J4,3= J4,5= 1 . 5 , 5 4 , 6 = l),2.75 (ddd, H-6, J6,7 = 5, J5,6 = 8, J66,4= l),2.16 (dq, H-3, J3,8= 5.8, J3,2 = J3,4 = 53,s = 1.51, 1.82 (dt, H-5, J5,6 = 8, J5,4 = J5,3 = 1-51,1.23 (m, H-7, 57,s = J7,ga = 8, J7,%= 4, J7,6= 5), 0.90 (m, H-8, J8,3 = J8,7 = 8, J8,ga = Je,gs = 4), 0.52 (dt, H-ga, Jga,8 = J9,,7 = 8, J ~ , =A5), 0.28 (4,H-98, J%,ga = 5 , J4s,7= J9s,8 = 4); MS, m l e 260, 245, 228, 200,169, 141, 129, 115. (d) Adduct 12: CH3C4~lo
CH,CO, Y
l
perature with 622 mg (6.77 mmol) of CHT and 555 mg (3.18 mmol) of enophile in CH2C12solution (1.5 mL). After reaction, the content of the reaction tube was analyzed by GLC and submitted to the usual workup. The high-pressure runs were shown to contain three compounds which were separated by column chromatography followed by preparative-layer chromatography (with ether-hexane (2:l) as eluent). The first compound was proved to be 16, diethyl hydrazine-l,Zdicarboxylate(mp 131-132 tR 12.9; Rf 0.11) by comparison with a commercial sample (Fluka). The other compounds were shown to be the ene adduct 14 already reportedlQ(tR 19.3; Rf 0.36) and the unprecedented norcaradiene adduct 15 (tR 19.3; Rf 0.29): IR (CDCl,) 3070,3005, 1730,1530 cm-'; NMR (numeration as for 9) 6.23 and 5.97 (t,H-4 and H.5, J4,5= 8), 5.20 and 5.12 (br, H-3 and H-6), 4.22 (q, OCH2), 1.77 and 1.61 (br, H-7 and H-8), 1.26 (t,CH3),0.42 (4, H-ga, Jgk% = 6, Jga,7 = Jga,8 = 7), 0.13 (dt, H-9, J%,ga = 6, J Q S , ~ = J g s , ~= 3.5); MS, m l e 266, 176, 93. Anal. Calcd for Cl3Hl8O4N2:C, 58.63; H, 6.81; N, 10.52. Found: C, 58.59; H, 6.74; N, 10.53. 6. Reaction with Dimethyl Mesoxalate. The high-pressure procedure (900 MPa) was repeated with a CHzClzsolution of 622 mg (6.77 mmol) of CHT and 920 mg (6.29 mmol) of dimethyl mesoxalate at 80 "C during 24 h. The yield of products was 72%. GLC analysis showed the formation of two compounds (955). Column chromatography with ether-hexane (2:l) as eluent gave a slightly yellow solid 17 (tR 16.6; Rf 0.40; mp 76-78 "C): IR (KBr) 3500,1750,1620cm-'; NMR (CDCld 6.71 (t,2 H, C=C), 6.25 (dm, 2 H, C=C), 5.27 (dd, 2 H, C=C), 4.06 (br, 1 H, OH), 3.82 (6, 6 H, OCH,); MS, m l e 238, 220, 147, 119, 91. Anal. Calcd for C12H1405: C, 60.50; H, 5.92. Found: C, 60.70; H, 6.17.
"c;
N
-
"&COzCH3 4 2
589
1,2
*
solid, mp > 300 "c; tR 25.0; IR (CDClJ 3030, 3000, 1720, 1590 cm-'; NMR (concerningcoupling constants, see note for product 10) 7.41 (d, H-12), 6.42 (dd, H-lo), 5.86 (d, H-ll),3.73 and 3.71 (8, OCH, on C-11 and C-13), 3.66 (s, OCH, on C-l), 3.15 (dt, H-2), 2.98 (br, H-4), 2.81 (ddd, H-6), 2.24 (dq, H-31, 1.91 (dt, H-51, 1.60 (m, H-7, J7,Q= 3), 1.49 (dt, H-9, J S ,=~10, ~ J9,7 = J9,8 = 3), 1.25 (m, H-8, J8,7= 8, J8,3= 5.8, J8,9= 3); MS, m l e 344,277,252,237, 225, 193, 165,152,128,115. 5. Reaction with Diethyl Azodicarboxylate. The low- and high-pressure procedures were repeated as above a t room tem-
Acknowledgment. We thank Dr. A Rahm (University of Bordeaux I) for performing the 1100-MPa r u n (isomerization attempt of 5)) Dr. R. Breault for linguistic assistance, a n d E. Schleiffer for GC analyses. Registry No. 1,31456-54-9;2,54382-95-5;exo-3,100191-06-8; endo-3, 31576-25-7; 4,5932-77-4;5, 100191-07-9;'9,100191-08-0;
10,100191-09-1; 11,100191-10-4;12,100191-11-5; 14,100191-12-6; 15,iooi91-13-7; 16,4114-28-7; i7,iooi9i-i4-a;TCNE, 670-54-2; CHT, 544-25-2; 8,8,9,9-tetracyanotricyclo[3.2.2.02~4]non-6-ene, 16118-23-3; acrylonitrile, 107-13-1; dimethyl acetylenedicarboxylate, 762-42-5;methyl propiolate, 922-67-8;diethyl azodicarboxylate, 1972-28-7;dimethyl mesoxalate, 3298-40-6.
Induction of the Cholesteric Mesophase in Nematic Liquid Crystals: Correlation between the Conformation of Open-Chain Chiral 1,l'-Binaphthyls and Their Twisting Powers Giovanni Gottarelli* a n d Gian Piero Spada Zstituto di Scienze Chimiche, Universita' di Bologna, 40127 Bologna, Italy
Richard Bartsch, G u y Solladig,* a n d Richard Zimmermann Ecole Nationale Superieure de Chimie, Uniuersite' Louis Pasteur, 67008 Strasbourg, France Received November 12, 1985
The twisting powers PM of 10 optically active open-chain 2,2'-disubstituted 1,l'-binaphthyls of known absolute configuration were measured in biphenyl nematic liquid crystals. The results show that it is possible to correlate the conformation (cisoid or transoid) of the optically active compounds to the sign of their twisting powers: for the absolute configuration S, a positive & value corresponds to a cisoid conformation while a negative pM value corresponds to a transoid conformation. These conformational conclusions were in agreement with CD and X-ray data. Induced cholesteric mesophases a r e generated b y t h e addition of traces of chiral compounds to nematic liquid
(1) Friedel, G.Ann. Phys. (Paris) 1922, 18,273-474.
0022-3263/86/1951-0589$01.50/0
Different substances show a different ability t o twist a nematic phase. T h e twisting power of chiral dopant can (2) Buckingham, A. D.; Ceasar, G. P.; Dunn, M. B. Chem. Phys. Lett. 1969, 3, 540.
0 1986 American Chemical Society
